There is a common misperception that charging one's battery banks faster is better or that having more charging capacity guarantees faster charging. Here are some reasons it is not always true:
Lead batteries have a maximum amount of current they will accept, typically C/3 for AGM and C/5 for flooded. So if you have 100Ah of AGM the most it will want to take is something like ~33A. Once the battery's limit is hit throwing more charging capacity at it can't charge it any faster.1)
Deep-cycled lead batteries have a lengthy Absorption stage that cannot be sped up2). Depending on use, Absorption typically requires several hours.There is a saying that “it takes 9 months to make a baby, but two women cannot make a baby in 4.5 months”. Same with absorption - it takes what it takes and you cannot hurry it in the normal sense.
charge current affects the SOC transition point from bulk to absorption charging - MaineSail3)
MaineSail found that
Note that the using 2x the charging current only sped up the whole process by 12 minutes (3.6%) due to Vabs starting earlier but taking longer.
Lithium batteries can slurp up current wildly, but shouldn't for their own health. Lithium lasts longest in sub-C use (ie, less than 100A for a 100Ah Li bank). C/2 (50A) is a more common manufacturer recommendation, and folks striving for added longevity might limit it to C/5 (20A). . In commercial examples the BMS will limit current to protect the cells. A small DC-DC charger can help protect bare cells from their own greediness.
Limiting charging current also makes it easier on alternators when they are used to charge Li.